TABLE 5

The ratio of the log KB value for CGP12177 (as an antagonist of cimaterol) and log EC50 value for CGP12177 for responses seen at the β2-WT and β2-TM chimeric receptors (data taken from Table 4)

Ratios of the affinity for antagonists at the two conformations are also given (i.e., log KB for antagonism of cimaterol/log KB for antagonism of CGP12177). This table examines the ratio of the affinities of ligands at the β2-adrenoceptor and thus allows for differences in absolute affinity. ICI118551 has lower affinity at the β2-TM4 receptor (Table 4), but this occurred both in the presence of cimaterol and CGP12177; thus, the ratio is similar to that at the other receptors. There is no large consistent change with any of the receptors.

Ratio of Log KB CGP12177/Log EC50 CGP12177Ratio of Log KB (Cimaterol as Agonist)/Log KB (CGP12177 as Agonist)
CGP20712ABisoprololICI118551Propranolol
β2-WT0.65−0.090.250.250.63
β2-TM10.260.460.190.230.49
β2-TM20.810.410.250.270.55
β2-TM30.810.360.520.240.86
β2-TM40.630.040.410.451.00
β2-TM50.510.160.060.190.71
β2-TM60.78−0.260.330.470.41
β2-TM70.010.350.470.090.28